I defiantly say it is Brett; just think about it for a moment. He is about the only guy that appeared in this show where Patrick Jane humiliates (yes I know Jane humiliates everyone, but this guy was the only one who gets bullied by Jane who works in the police). Also, he is about the only one that everyone agreed is stupid, Jane makes fun of everyone, but Teresa, Wayne and Kimball all looked at each other in a smirking kind of way (they show us he is an idiot without saying). And in any criminal cases the killer has to have a motive and what better motive than revenge on everyone because they made fun of him (don't tell me you don't know that about Brett, because with that kind of personality everyone will make fun of you). In addition he was probably the only guy Patrick hated and showed his hater for. Also, he is just too stupid! I can't imagine a guy like him being a head of analyzing methods of killing with being this of a fool, which only suggests that he is smarter than he looks -don't forget don't judge a book by its cover. Lastly, he fits in all the clues in the list. One final word, being a fool makes anyone dismiss him from killing anyone without even looking deep into it, and remember Jane didn't even try to analyze him, he just made of him and went. And you never know :p
